1990 240sx, KA24E 50,000 km's on rebuild, 187,000 on chasis
The car was running a little rough before and idle, nothing too bad, just the odd missfire once every 30 seconds or so. I figured it just needed a tune up.
anyways, I was checking the compression on the motor today and it all checked out fine. 150 across the board
however after putting all the plugs and wires back, the car ran like a three legged turtle. running on 3 cylinders at idle, and smoothing out past 2500 rpm. if I jabbed the gas it was a clear and evident missfire. While idling I pulled the plugs one at a time to determine which cylinder was acting up... Number 2.
I could see the spark jumping from the plug wire, so I've got spark. Compression just checked out fine... I thought it must be the injector!
The injector on #2 had been leaking a little, but not that bad really. To determine if it was the injector I swapped it for the #1 and put everything back. engine ran really bad at first till the gas started flowing proper again, but now it idles a little high (900 or so) and it still runs like crap when I get on the gas. Worst of all.. #2 is still missing consistantly.
any ideas? ECU? Dizzy?(can't really see that being the prob) injector harness?
I'm completely stumped. I'm going to do another comp check tommorrow to make sure I didn't bugger up a valve or something somehow.
Compression Check... now Cyl 2 isn't working
Re: Compression Check... now Cyl 2 isn't working (pwjm)
Seeing a visible spark jumping from your wire is not normal.You must have a crack in the protective wire cover and the spark is jumping from the wire to the valve cover or something and causing misfire.
Re: Compression Check... now Cyl 2 isn't working (Razi)
no, i mean with the plug connected to it and out of the block, I can see a spark. my bad.
as well, I can hear the spark arcing to the plug when pulling the wire off and on while the car is running.
The wires are relatively new and in good shape. The car is getting more than enough spark to Cyl 2. even if it was getting a weak spark it wouldn't account for the complete lack of firing on that cylinder at idle.
as well, I can hear the spark arcing to the plug when pulling the wire off and on while the car is running.
The wires are relatively new and in good shape. The car is getting more than enough spark to Cyl 2. even if it was getting a weak spark it wouldn't account for the complete lack of firing on that cylinder at idle.
Re: Compression Check... now Cyl 2 isn't working (pwjm)
Hmm...check for vacuum leaks.
My car had a random misfire once every few seconds and would misfire badly under load.It turned out to be a vacuum leak and my bad intake setup (I have a turbo KA and had to fabricate some odd bits to get a working intake setup).After fixing some vacuum leaks and boost leaks and modifying my intake box and putting in a better filter it runs perfectly now.
Anyways. Haha.Check if you have a vacuum leak anywhere.Start the car up and spray soapy water on vacuum hoses and see if the water starts bubbling.
I don't think it's your distributor since you're getting spark just fine.
Also, another trouble shooting tip. With the car running, unplug the harness on injector #2 and if nothing changes, check the injector harness and grounds. Also, I would check all the injector o-rings. Replace any damaged ones and coat the o-rings with Vaseline before putting them back into the fuel rail. If they don't go in easily, coat more Vaseline on them until they pop in easily. This prevents you from damaging the o-rings while putting them back in.
My car had a random misfire once every few seconds and would misfire badly under load.It turned out to be a vacuum leak and my bad intake setup (I have a turbo KA and had to fabricate some odd bits to get a working intake setup).After fixing some vacuum leaks and boost leaks and modifying my intake box and putting in a better filter it runs perfectly now.
Anyways. Haha.Check if you have a vacuum leak anywhere.Start the car up and spray soapy water on vacuum hoses and see if the water starts bubbling.
I don't think it's your distributor since you're getting spark just fine.
Also, another trouble shooting tip. With the car running, unplug the harness on injector #2 and if nothing changes, check the injector harness and grounds. Also, I would check all the injector o-rings. Replace any damaged ones and coat the o-rings with Vaseline before putting them back into the fuel rail. If they don't go in easily, coat more Vaseline on them until they pop in easily. This prevents you from damaging the o-rings while putting them back in.
Re: Compression Check... now Cyl 2 isn't working (Razi)
unplugging the inj harness on that cyl wont make a difference... thats what I've been saying all along. With the car at Idle I can take off the plug wire and it runs exactly the same. Same goes for the injector I would imagine...
It only seems to smooth out once the revs pick up, but that doesn't really mean that that cylinder is working at all, everything is just moving faster so it seems smoother.
I'll look over the harness as best as I can in the dark right now (I'm stranded at my friends house) but this is really confusing the crap out of me.
If I try to drive the car like this can I bugger the engine? I'm afraid of it going lean due to a faulty injector/bad signal.
How the hell could this happen in teh first place? All I did was unplugged the wires and plugs one at a time and checked the compression....
Modified by pwjm at 9:27 PM 9/18/2009
It only seems to smooth out once the revs pick up, but that doesn't really mean that that cylinder is working at all, everything is just moving faster so it seems smoother.
I'll look over the harness as best as I can in the dark right now (I'm stranded at my friends house) but this is really confusing the crap out of me.
If I try to drive the car like this can I bugger the engine? I'm afraid of it going lean due to a faulty injector/bad signal.
How the hell could this happen in teh first place? All I did was unplugged the wires and plugs one at a time and checked the compression....
Modified by pwjm at 9:27 PM 9/18/2009
Re: Compression Check... now Cyl 2 isn't working (pwjm)
Not sure how that would have happened.
I wouldn't advise you to drive it in the current condition.
An odd problem...
I wouldn't advise you to drive it in the current condition.
An odd problem...
Re: Compression Check... now Cyl 2 isn't working (Razi)
Well, got the problem sorted... for now.
I thought, screw it, for the price its worth a shot. I bought new plugs, wires, cap and rotor. Even though #2 was getting spark I figured what the hell...
We also tested the injector harness. It was corroded a little but so we scuffed it up a but to make better contact. The weird thing was though, #1 wasn't getting any voltage at all when cranking the engine over. #2,3, 4 all got 4-6 volts. Not #1 though.
Deciding to deal with one problem at a time, in this circumstance #2 not firing, I bought new injector O-rings and the tune up parts mentioned earlier. Installed everything and now the engine idles and runs fine!
I noticed a lot of future headaches though. Some wire casings had been worn through from rubbing. No wires are exposed yet, but its not good either way. I tapped it up and moved it as best as I could.
Anyone have any idea why the #1 injector plug wasn't getting any voltage? It runs fine now so It must be working. Just couldn't get anything off it with the multimeter.
I thought, screw it, for the price its worth a shot. I bought new plugs, wires, cap and rotor. Even though #2 was getting spark I figured what the hell...
We also tested the injector harness. It was corroded a little but so we scuffed it up a but to make better contact. The weird thing was though, #1 wasn't getting any voltage at all when cranking the engine over. #2,3, 4 all got 4-6 volts. Not #1 though.
Deciding to deal with one problem at a time, in this circumstance #2 not firing, I bought new injector O-rings and the tune up parts mentioned earlier. Installed everything and now the engine idles and runs fine!
I noticed a lot of future headaches though. Some wire casings had been worn through from rubbing. No wires are exposed yet, but its not good either way. I tapped it up and moved it as best as I could.
Anyone have any idea why the #1 injector plug wasn't getting any voltage? It runs fine now so It must be working. Just couldn't get anything off it with the multimeter.